Add support for `pypy_73`-style tags (#10660)
## Summary
I'm inferring that these are like... the older tag format? See, e.g.:
```
soxbindings-0.0.1-pp27-pypy_73-macosx_10_9_x86_64.whl
soxbindings-0.0.1-pp27-pypy_73-manylinux2010_x86_64.whl
soxbindings-0.0.1-pp36-pypy36_pp73-macosx_10_9_x86_64.whl
soxbindings-0.0.1-pp36-pypy36_pp73-manylinux2010_x86_64.whl
```
